examples: improve the pendulum simulation, with several modes and diagrams (#13446)

examples/pendulum-simulation/modules/sim/worker_test.v

@@ -0,0 +1,63 @@
+module sim
+
+const (
+	worker_test_mock_params = SimParams{
+		rope_length: 0.25
+		bearing_mass: 0.03
+		magnet_spacing: 0.05
+		magnet_height: 0.03
+		magnet_strength: 10
+		gravity: 4.9
+	}
+	worker_test_mock_state = SimState{
+		position: vector(
+			x: -0.016957230930171364
+			y: -0.02937078552673521
+			z: 0.002311063475327252
+		)
+		velocity: vector(
+			x: -7.251158929833104
+			y: -12.559375680227724
+			z: -105.91539687686381
+		)
+		accel: vector(
+			x: -8.337034766251843e-11
+			y: -2.842170943040401e-10
+			z: 1.2126596023639044e-10
+		)
+	}
+)
+
+fn test_compute_result() {
+	request := SimRequest{
+		id: 0
+		params: sim.worker_test_mock_params
+		state: sim.worker_test_mock_state
+	}
+	expected_state := SimState{
+		position: vector(
+			x: -0.01695723093017133
+			y: -0.02937078552673517
+			z: 0.002311063475327252
+		)
+		velocity: vector(
+			x: -7.251158929832518
+			y: -12.559375680226692
+			z: -105.91539687685668
+		)
+		accel: vector(
+			x: -3.789561257387201e-12
+			y: 3.410605131648481e-11
+			z: 3.031649005909761e-11
+		)
+	}
+	expected := &SimResult{
+		state: expected_state
+		id: 0
+		magnet1_distance: 0.07993696666249224
+		magnet2_distance: 0.07993696666249223
+		magnet3_distance: 0.03609361938278009
+	}
+	result := compute_result(request)
+	assert result == expected
+}